Spreader stoker apparatus



y 1, 1948. D. J. MOSSHART 2,441,366

SPREADER STOKER APPARATUS Filed Oct. 8, 1945 INVENTOR Donnua J. MOSSHRRT- ATTORNEY Patented May 11, 1948 SPREADER STOKER APPARATUS Donald J. Mosshart, Ardmore, Pm, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 8, 1945, Serial No. 821,080

11 Claims. (01. 110-101) This invention relates to furnace controls, more particularly to controls for maintaining a fuel bed of predetermined thickness characteristics,

- bed in response to changes in the ratio of rates of flow of primary air to various sections of the fuel bed.

Yet another object of the invention is to provide, in a "spreader type stoker, control mecha-- nism for varying the trajectories of fuel being "spread on the fuel bed in response to changes in the ratio of rates of flow of primary air to different portions of the fuel bed.

These and other objects are effected by the invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of thisapplication, in which:

Fig. 1 is a diagrammatic view, partially in section, of stoker apparatus embodying the principles of the present invention; and

Fig. 2 is an enlarged fragmentary view of a modification of a portion of the structure shown in Fig. 1

Referring now to the drawing more in detail, reference character I indicates, in-its entirety, a stoker installation of the spreader and the "sprinkler type, together with a chain grate type of fuel-supporting surface disposed in the bottom of a furnace between the front wall ii and the rear wall l2 of the latter.

The fuel-feeding mechanism comprises a hopper 13 and one or more rams ll adapted to feed fuel from the hopper rearwardly through a fuel compartment 15 and over the rear discharge edge of a spill plate ii, the position of the latter being adiustabie in a front to rear direction by suitable means, such as an operating rod I'l'. The fuel, pushed rearwardly by the ram II and falling by gravity from the rear discharge edge of the spill plate I, is struck by the blades l8 of the rotary impeller 19 and is projected rearwardly through the opening 2i in the furnace front wall to fall through the atmosphere about the chain grate 22, the fine fuel being burned in suspension and the larger particles thereof falling to the grate surface where they are consumed during the time they are being carried by the moving grate surface to the ash pit 25, below the rear discharge end oi. the chain grate. The chain grate operates in the usual manner, being carried by sprockets 23 and 24 and serving to progressively advance the fuel from the vicinity of the front wall II to the ash pit 25 beneath the furnace rear wall l2.

Wall structure, such as shown at 26, 2! and 28 serves to define a main plenum chamber 29, positioned beneath the effective area of the chain grate 22. Partition members 3! and 32 are dis posed within the main plenum chamber 29 in such a manner as to divide a portion of the interior of the latter into two secondary plenum chambers A and B. This partition structure 3i 32 is provided with inlet orifices 33 and 3 for the secondary plenum chambers A and B, re spectively, for admission of air to the latter from the main plenum chamber 29, this air being provided from any suitable source such as the can" trii'ugal blower 35. Supplementary partition members it, ill and 38 are positioned within the grate structure between the upp r and lower courses thereof, and constitute, in effect, continuations of the wall and partition members 26, 32 and 21, respectively, with the result that the secondary plenum chamhere A and B extend upwardly to the under surface of the upper course of the chain grate 22. While in the construction herein illustrated the orifices 33 and 34, providing for admission of primary air to the secondary plenum chambers A and B, are of fixed sizes, it will be obvious that they maybe made adjustable in effective crosssectional area, if desired, in order to obtain any desired ratio of rate of flow of air to the two zones of the fuel bed overlying the plenum chambers A and B.

It will be apparent that, with the orifices 33 and 34 of fixed effective cross-sectional area, or of any predetermined cross-sectional area, the rate of flow of air to the plenum chambers A and B will be dependent upon the thickness of the fuel bed areas overlying the two plenum chambers. If for any reason the thickness of the fuel bed section overlying the plenum chamber B, for example, should become materially thinner than the fuel bed section overlying the chamber A, a relatively greater quantity of air would pass through the chamber 13, thereby resulting in excess combustion of fuel in the fuel bed section overlying the chamber B, thus further thinning the fuel bed and increasing the urn balanced condition existing between the two sections of fuel bed.

It is the purpose of the present invention to provide novel means for counteracting or eliminating such unbalanced conditions and to this end there is provided control apparatus, indicated in its entirety by the reference character 40.

A pair of diaphragms 4| and 42 are housed within casings 43 and 44, respectively, the spaces at the upper sides of the diaphragms 4i and 42 being in communication, through conduits 45 and 41, respectively, with the interiors of the plenum chambers A and B, with the result that changes in the pressures existing within these plenum chambers will be transmitted to the diaphragms to cause movement of the latter.

Any such movement of the dlaphragms 4| and 42 is transmitted through rods 48 and 49, respectively, to a link 50, fulcrumed at i to a fixed support 52. The rods 48 and 49 are pivotally connected to the link 50 at opposite sides of the fulcrum 5|, as at 53 and 54, respectively.

One end of the link 50 is pivotally connected, at 55, to the free end of arm 56 of a bell crank 51, pivotally mounted as at 58, on a fixed support 59. The other arm 5| of the bell crank carries a single-pole, double-throw mercury switch 62.

The mercury switch 62 controls a circuit, indicated in its entirety by a reference character 63, which conveys electric power from a source S to a reversible motor 64, this motor constituting the driving means for a gear box 55 which operates a rheostat 56 disposed in the circuit 51 which supplies power from the source S to a variable speed motor 68, this motor continuously rotating the rotary impeller 19 of the spreader stoker. Preferably, the gear box 55 has an input to output ratio which will require the consumption of several minutes (5 to for adjustment of the rheostat through its entire range to vary the speed of the impellerv driving motor 68 from minimum to maximum R. P. M.

In operation, if the fuel bed section overlying the plenum chamber B becomes thinner than that overlying the plenum chamber A, for any reason, such as change in the size or moisture content of the fuel, the ratio of air pressures within the chambers A and B will be consequently varied, the pressure in the chamber B decreasing and resulting in upward movement of the diaphragm 42 and consequent tilting of the link 50 with the end 55 thereof moving downward so that the mercury in the switch 62 will flow to the right-hand end thereof as viewed in Fig. 1. This will energize that part of the circuit 63 which causes the I motor 64 to rotate in a direction tending to decrease the resistance of the rheostat 66 with consequent increase in the speed of the variable speed motor 68. Due to the low gear ratio of the gear box 55, several minutes will be consumed in the gradual speeding up of the motor 68 and of the rotary impeller l9. As the revolutions of the rotary impeller is increase, the blades l8 thereof will contact, with heavier impacts, the fuel fed from the rear discharge edge of the spill plate, resulting in increased trajectories of the fuel entering the furnace and disposition of the fuel at points nearer the rear of the chain grate. As the speed of the rotary impeller increases, the fuel will be deposited farther and farther rearwardly on the chain grate until the greater portion of the fuel is being deposited on the portion of the fuel bed overlying the plenum chamber B, with the result that the thickness of that section will increase to a point where the resistance to flow of air therethrough from the chamber B is greater than the resistance to flow of air from the chamber A. When this condition is reached, the air pressure in the chamber A will be lower than that in the chamber B and the action of the diaphragms 4| and 42 and of the linkage controlled thereby will cause reversal of the position of the mercury switch 52 with consequent reversal of gear box input motor 54 and reversal of the direction of the movement of the rheostat 68. This will result in a gradual slowing down of the rotary impeller driving motor 58 and the consequent shortening of the trajectories of the fuel impelled by the rotary impeller until such time as the air balance between the two plenum chambers again reverses.

If it is desired to maintain a thicker fuel bed on the portion of the grate overlying one plenum chamber than on the portion overlying the other chamber, this may be obtained by adjustment of the location of the fulcrum 5| by proper selection of the pivot hole 50 in the link 50 for reception of the fulcrum 5|.

In Fig. 2, there is illustrated a modification of the fuel trajectory-varying mechanism, wherein the rotary impeller l9 rotates at a predetermined speed and variation of the trajectories is obtained by adjustment of the front to rear position of the spill plate I5. Obviously, if the spill plate i5 is moved forwardly or to the left as viewed in Fig. 2, the blades l8 of the rotary impeller will tend to strike the fuel before the blades have reached a vertical position, with the result that the trajectories of the fuel are higher and the fuel thrown well to the rear of the grate surface. On the other hand, if the spill plate i6 is moved rearwardly or to the right as viewed in Fig. 2, the blades i8 will have passed a vertical position before striking the fuel falling from the rear discharge edge of the spill plate, with the result that the trajectories of the fuel will be substantially below the horizontal with the fuel falling on the forward portion of the grate.

With this control, a circuit 53', corresponding to the circuit 63 of the previously-described arrangement, is controlled by diaphragms, linkage and mercury switch arrangement similar to that shown in Fig. 1. The circuit 83' likewise serves to reverse the motor 68 driving a gear box II which in turn works through a worm gear drive 12-13 carried by the shaft 14 of the spill plate I B to move the latter forwardly or rearwardly, depending on the direction of rotation of the motor 68. As in the arrangement f Fig. 1, the gear box input to output speed ratios are such that several minutes will elapse for complete travel of the spill plate in any one direction.

In order to limit forward or rearward positions of the spill plate IS, the rod 14 carries a pair of spaced contacts 15 and 15, disposed at opposite sides of a contact ll. When the spill plate l5 reaches its forward limit of movement the element 15 will contact the element 11 and close the circuit 18 to energize the solenoid 19, thus opening the switch 8| in the part of the circuit 63 which is energizing the reversible motor 68, to cause forward movement of the spill plate [6. With this part of the circuit 53 open, the motor 68 will be idle and the spill plate I will remain in its forwardmost position until change in the air pressure ratio of the two plenum chambers results in change in position of the mercury switch and consequent energiza tion of the other half of the circuit 53', causing energization of the motor for rotation in the opposite direction, whereupon the spill plate It will be moved forwardly or to the left. As soon as the spill plate moves to the left. the contact between the elements 15 and 11 is broken, the solenoid I9 deenergized and the switch 8! closed, with the result that the part of the circuit 63' which includes the switch M will be ready for use upon further change in the air balance of the con trol system.

Movement of the spill plate to the left or forward is likewise limited by engagement of contacts l and 11 to energize the solenoid 82 and open the switch 83.

While the invention has been illustrated as applied to a chain grate type of stoker, it will be apparent that it may be used to equal advantage with any type of fuel-supporting surface.

While the invention has been shown in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof.

What is claimed is:

1. Apparatus of the character described, con prising means providing a fuel-supporting surface, means providing a pair of plenum chambers beneath said fuel-supporting surface, fuel-feeding mechanism of the spreader" or sprinkler type for feeding fuel to said fuel-supporting surface through the atmosphere thereabove, and means for automatically varying the ratio of the quantity of fuel fed to the surface overlying one of the plenum chambers to the quantity of fuel fed to the surface overlying the other plenum chamber in response to changes in the ratio of thickness of the fuel bed overlying the two plenum chambers.

2. Apparatus of the character described comprising means providing a fuel-supporting surface, means providing a pair of plenum chambers beneath said fuel-supporting surface, means for supplying air to said plenum chambers, means for spreading fuel on said fuel-supporting surface through the atmosphere thereabove, and means for automatically shifting the deposition of the majority of fuel fed by said fuel-spreading means from one portion of said fuel-supporting surface to another portion thereof in response to changes in the ratio of the rate of flow of air to one plenum chamber to the rate of flow of air to the other plenum chamber.

3. Apparatus of the character described comprising means providing a fuel-supporting surface; means cooperating with said first-mentioned means to provide below the latter a pair of plenum chambers; fuel-feeding means of the "spreader type, disposed externally of the vertical projection of said fuel-supporting surface, for spreading fuel onto a portion of said fuelsupporting surface through the atmosphere thereabove; and means, responsive to changes in the ratio of air pressures in the two plenum chambers, to shift the deposition of fuel fed by said fuel-feeding means from one portion of said fuel-supporting thereof.

4. Apparatus of the character described comprising means providing a fuel-supporting surface; means cooperating with said first-mentioned means to provide below the latter a pair of plenum chambers; fuel-feeding means of the spreader type for projecting fuel onto y, portion of said fuel-supporting surface through the atmosphere thereabove, said fuel-feeding means surface to another portion 7 including a rotary impeller and means for rotating the latter at varying speeds, whereby the trajectories of the fuel projected thereby onto the fuel-supporting surface are varied, with corresponding variations in the area of the fuel-supporting surface on which the fuel is spread; and

means responsive to changes in the ratio of air pressures in the two plenum chambers resulting from changes in the relative resistance of the two portions of fuel bed, overlying the two plenum chambers, to flow of air therethrough from said plenum chambers, to automatically vary the speed of rotation of the rotary impeller.

5. Apparatus of the character described comprising means providing a fuel-supporting surface; means cooperating with said first-mentioned means to provide below the latter a pair of plenum chambers; fuel-feeding means for projectlng fuel onto a portion of said fuel-supporting surface through the atmosphere thereabove, said fuel-feeding means including a rotary impeller and a variable speed engine for rotating the impeller at various speeds, whereby the trajectories of the fuel propelled thereby onto the fuel-supporting surfac may be varied with corresponding variation in the area of the fuel-supporting surface on which the fuel is spread; means for supplying constant ratios of volumes of air to the two plenum chambers for discharge through the bed of fuel thereabove; and means, responsive to changes in the relative resistances of the portions of the fuel bed overlying the two lenum chambers to flow of air therethrough, to vary the speed of the engine driving the rotary impeller.

6. Apparatus-of the character described comprising means providing a fuel-supporting surface having first and second zones; means cooperating with the first-mentioned means to provide below the latter first and second plenum chambers associated with the first and second zones of the fuel-supporting surface, respectivell; fuel-feedin mechanism disposed beyond one end of the first zone of the fuel-supporting surface, with the second zone extending from the opposite end of the first zone, said fuei-impelling mechanism being adapted to impel fuel onto the two zones through the atmosphere thereabove, said fuel-feeding mechanism including means for varying the impelling force exerted by said mechanism on the fuel from a minimum to a maximum, whereby when minimum force is exerted, the fuel is deposited on the first zone of the fuel-supporting surface and when maximum force is exerted, the fuel is deposited on the sec- 0nd zone; means for supplying air to the two plenum chambers at constant pressures, for discharge through the fuel thereabove; and means responsive to changes in the ratios of the pressures within the two plenum chambers, which changes result from variations in the resistance of the fuel thereabove to flow of air therethrough, for varying the impelling force exerted on the fuel being fed by the fuel-feeding mechanism, to vary the relative quantities of fuel deposited on the two zones in inverse relation to the changed pres sure relations in the two plenum chambers there- I below.

7. Apparatus of the character described comprising means providing a fuel-supporting surface having first and second zones disposed in end-to-end relation; fuel-feeding mechanism disposed in longitudinal alignment with the two fuelsupporting surface zones and including an impeller rotatable about a horizontal axis and adapted to spread fuel on the first zone through the atmosphere thereabove and on the second zone through the atmosphere above both zones, and means for rotating said impeller at speeds variable between a minimum speed at which the majority of the fuel is spread on the first zone and a maximum speed at which the majority of the fuel is spread on the second zone; and means responsive to changes in the relative thicknesses of the fuel beds on the two zones for varying the speed of rotation of the rotary impeller and consequently the area of the fuel-supporting surface on which the fuel is deposited to return the fuel bed thicknesses to their original ratio.

8. Apparatus of the character described comprising means providing a fuel-supporting surface having first and second zones disposed in end-to-end relation; means cooperating with the first-mentioned means to provide below the latter first and second plenum chambers communicating with the first and second zones, respectively, of the fuel-supporting surface; fuelfeeding mechanism disposed in longitudinal alignment with the two zones of the fuel-supporting surface and including an impeller rotatable about a horizontal axis and adapted to spread fuel on the first zone through the atmosphere thereabove and on the second zone through the atmosphere above both zones, and means for rotating said impeller at speeds variable between a minimum at which the majority of fuel is spread on the second zone; means for supplying constant ratios of volumes of air to the two plenum chambers for discharge therefrom through the beds of fuel on the two zones thereabove; and means, responsive to changes in the ratio of air volumes supplied to the two plenum chambers resulting from changes in the ratio of thicknesses of the fuel beds overlying the two plenum chambers, for controlling the driving means for the rotary impeller to vary the rotative speed of the latter, whereby the deposition of fuel is shifted from one zone of the fuelsupporting surface to the other zone thereof to return the fuel bed thicknesses to their original ratio.

9. Apparatus of the character described comprisin means providing a fuel-supporting surface having first and second zones disposed in end-to-end relation; fuelfeeding mechanism aligned with the two zones of the fuel-supporting surface and including means for projecting fuel to the first zone through the atmosphere thereabove and to the second zone through the atmosphere above both zones, and means for varying the trajectories of the fuel as they are projected to the zones of the fuel-supporting surface, whereby with decreasing trajectories, the majority of the fuel is deposited on the first zone and with increasing trajectories an increasingly larger portion of the fuel is deposited on the second zone; and means, responsive to changes from desired relative thicknesses of the fuel beds on the two zones, for adjusting the trajectory-varying means to vary the location on the fuel beds of the deposition of the majority of the fuel to reestablish the desired relative thicknesses of fuel beds on the two zones.

10. Apparatus of the character described comprising means providing a fuel-supporting sur face; means cooperating with the first-mentioned means to provide beneath the latter a pair of plenum chambers, one of which is adapted to discharge air through the fuel bed on a first zone of the fuel-supporting surface thereabove and the other of which is adapted to discharge air through the fuel bed on a second zone of the fuel-supporting surface thereabove; fuel-feeding mechanism including means for proiectinz fuel to the first zone through the atmosphere thereabove and to the second zone through the atmosphere above both zones, and means for varying, between limits, the trajectories of the fuel particles as they are projected to the zones of the fuel-supporting surface, the limits being such that at the minimum the majority of the fuel falls on the first zone and at the maximum the majority of the fuel falls on the second zone; and means for controlling the trajectory-varying means, said last-mentioned means comprisin a speed reducer having an input shaft and an output shaft, a reversible motor adapted to drive said input shaft, means for reversing said motor in response to increases and decreases in the ratio of pressures in the two plenum chambers with respect to a selected ratio, and means operatively connecting the output shaft of the speed reducer with the trajectory-varying means, whereby with the reversible motor operating in one direction the fuel trajectories are gradually increased and with the motor operating in the other direction, the fuel trajectories are gradually decreased.

11. Apparatus of the character described comprising means providing a fuel-supporting surface having first and second zones disposed in end-to-end relation; fuel-feeding mechanism aligned with said two zones of the fuel-supporting surface and including an impeller rotatable about a horizontal axis, a spill plate disposed with its rear discharge edge overlying the rotary impeller and said spill plate being adjustable in front to rear directions with respect to a vertical plane containing the axis of rotation of the impeller, and means for feeding fuel along said spill plate for gravitational discharge from the rear discharge edge thereof to the rotary impeller therebelow, adjustment of the spill plate to a position with its discharge edge disposed forwardly of the vertical plane of the axis of rotation of the impeller producing high trajectories of fuel from the impeller with the majority of the fuel passing through the atmosphere above said first and second zones of the fuel-supporting surface and being deposited on said second zone, and adjustment of the spill plate to a position with its discharge edge disposed rearwardly of the vertical plane of the axis of rotation of the impeller producing relatively low trajectories of fuel from the impeller with the majority of the fuel passing through the atmosphere above said first zone of the fuel-supporting surface and being deposited thereon; and means, responsive to changes from the desired relative thicknesses of the fuel beds on the two zones, for adjusting the spill plate forwardly and rearwardly to vary the location on the fuel beds of the deposition of the majority of fuel beds, to reestablish the desired relative thicknesses of the fuel beds on said two zones.

DONALD J. MOSSHART.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

